The invention relates generally to transducer head assemblies for magnetic recording on rotating disk drives, and more particularly to self-loading negative pressure air bearing sliders for use with rotary actuators.
Magnetic head assemblies that fly relative to a rotating magnetic disk have been used extensively. Typically these heads comprise a slider upon whose trailing end a transducer is mounted. Slider designers would like to have the magnetic transducer fly as close to the disk as possible, and have the flying height be uniform regardless of variable flying conditions, such as speed variation from inside track to outside, seeks, and skew caused by rotary actuators. Flying height is viewed as one of the most critical parameters of non-contact magnetic recording.
As disk drives become increasingly compact, rotary actuators with short pivot arms are increasingly employed. However, these actuators increase the difficulty of flying height control because a rotary actuator causes the geometric orientation between the slider fixed to the pivot arm, and the disk rotation tangent, to change as the actuator moves the slider over the disk surface. A measure of this orientation is given by the skew angle 14 as shown in FIG. 1, which is defined as the angle between the slider's longitudinal axis and the direction of disk's tangential velocity. (The "wind" caused by disk rotation is approximately parallel to this tangent.) With the strive towards more compact disk drive packages for applications in smaller more portable equipment, the designer is motivated to use a short actuator pivot arm and thus create rather large skew angles.
However, conventional sliders are very sensitive to skew angle. Even with moderate skew angles in the 10-15 degree range, a conventional slider's fly height and roll angle (defined as the difference in flying height between the inside and outside rails, see FIG. 1b) are adversely influenced.
Increasing the skew angle at a fixed tangential velocity causes the slider pressure distribution to become distorted. This influences the net forces and torque acting upon the slider and results in both decreased flying height and increased roll. Because a transducer is located at the trailing edge of a rail (as is conventional) roll affects transducer performance because of greater flying height variations.
The effect of flying at a skewed angle also extends slider lift off thereby increasing wear and exacerbates the negative effects of rapid seek. Furthermore, conventional sliders are very sensitive to disk surface speeds. With linear actuation (skew angle is a constant 0.degree.), flying height is higher at outer disk radii. While this may be alleviated somewhat with optimized rotary actuator designs, the flying height is still dependent upon disk speed.
A conventional "zero load" or negative pressure air bearing ("NPAB") slider can achieve a flying height substantially independent of disk speeds. However, at skewed conditions, the NPAB exhibits excessive roll and average flying height loss because the downstream rail receives little air from the negative pressure cavity while at the same time the upstream rail is receiving air at ambient pressure.
The art needs a negative pressure air-bearing slider having a near constant, but low, flying height when used in conjunction with short arm rotary actuators and/or with high seek velocities wherein reading from a disk during seek is continued, for example, to read track addresses. Preferably, the slider will exhibit little or no roll over a wide variation in skew angles. The slider would also preferably have rapid take-of but still fly low at full speed.